In general, a weather strip is made of an excellent elastic rubber material and serves to maintain air-tightness.
The weather strip has been adapted to a motor vehicle as a body side weather strip mounted on a vehicle body panel of the motor vehicle, a door side weather strip (or referred to as a door weather strip) mounted to a door of the motor vehicle, and so on.
The door weather strip is mounted on a door panel along the entire circumference of the door so as to maintain air-tightness of a passenger side compartment when the door is closed and has a tight contact with a sealing surface of the vehicle body panel matching the door when the door is closed.
The door weather strip is overlapped with the vehicle body panel by a predetermined amount to improve the air-tightness when the door is closed.
When the door is closed so that the door weather strip is overlapped with the vehicle body panel, the door weather strip is elastically deformed from the original shape thereof and has the tight contact with the sealing surface of the vehicle body panel by virtue of an elastic repulsive force against a shape deformation thereof, thereby appropriately maintaining the air-tightness of the inside of the passenger compartment room even when the motor vehicle is being driven.
When the shape deformation, however, is repeatedly caused in the door weather strip due to the overlapping condition, the elastic force of the material of the door weather strip will be progressively reduced as time passes, and thus the air-tightness performance of the door weather strip will be deteriorated.
Furthermore, the repulsive force (or reaction force) of the door weather strip generated by the elasticity of the material thereof acts as an external force pushing the door in the open direction, thereby increasing the closing force of the door.
The closing force of the door means a magnitude of force needed to close the door, and which is a resultant force of a reaction force of the door weather strip and a locking force of components like a door latch, etc.
Therefore, the bigger the reaction force of the weather strip becomes, the greater the closing force of the door. As a result, a more strength and more rapid speed are required to close the door, and also the process of closing and opening the door may not be smoothly achieved.
Furthermore, the increased closing force of the door increases an operation noise of components related to a door locking operation, and opening operation sensitivity is deteriorated when the door is opened, thereby deteriorating a user's satisfaction.
Accordingly, when designing the door weather strip, a reaction force of the door weather strip has been determined considering the optimum level of the air-tightness performance and the closing force of the door, improving a simultaneously satisfaction on the air-tightness performance and the reasonable closing force of the door is difficult
The above information disclosed in this background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.